Systems and methods for additive manufacturing of three dimensional structures

ABSTRACT

A method of fabricating a three dimensional structure includes delivering a metal material to a printing site; and defining a microstructure of the metal material at the printing site by controlling the delivery of heating energy to the printing site and controlling the delivery of ultrasonic vibrations to the printing site.

BACKGROUND

The present disclosure relates generally to the field of additive manufacturing (also referred to as three dimensional (3D) printing). Additive manufacturing has become more prevalent in recent years as an option not only to rapidly produce prototypes, but also to manufacture final products. While more commonly used to produce polymer objects, current advances have allowed additive manufacturing to also be used to produce metal objects.

SUMMARY

One embodiment relates to a method of fabricating a three dimensional structure, comprising delivering a metal material to a printing site; and defining a microstructure of the metal material at the printing site by controlling the delivery of heating energy to the printing site; and controlling the delivery of ultrasonic vibrations to the printing site.

Another embodiment relates to a method of fabricating a three dimensional structure, comprising delivering a metal material to a printing site; delivering heating energy to the printing site; delivering a vaporizable coolant to the printing site; and defining a microstructure for the metal structure based on providing the heating energy to the metal material at the printing site and vaporizing the vaporizable coolant.

Another embodiment relates to a method of fabricating a three dimensional structure, comprising delivering a first metal material to a first printing site; delivering a first amount of heating energy to the first printing site; delivering a first vaporizable coolant to the first printing site; agitating the first printing site; and forming a first portion of a printed metal structure by providing the first amount of heating energy to the first metal material at the first printing site and vaporizing the first vaporizable coolant while agitating the first printing site.

Another embodiment relates to a system for fabricating a three dimensional structure, comprising a support for supporting the structure; a material delivery device configured to provide a metal material to a printing site; a heating energy delivery device configured to heat the material at the printing site; and a vibration delivery device configured to provide ultrasonic vibrations to the printing site.

Another embodiment relates to a system for fabricating a three dimensional structure, comprising a material delivery device configured to deliver a metal material to a printing site; a heating energy delivery device configured to deliver heating energy to the printing site; a coolant delivery device configured to deliver a vaporizable coolant to the printing site; and an ultrasonic vibration delivery device configured to deliver ultrasonic vibrations to the printing site.

Another embodiment relates to a method of forming a three dimensional structure comprising delivering material, heating energy, and vibrations to a first printing site to define a first grain structure at the first printing site; and delivering material, heating energy, and vibrations to a second printing site to define a second grain structure at a second printing site; wherein at least one of the delivered material, heating energy, and vibrations differs between the first and second printing sites to modify the second grain structure relative to the first grain structure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features descried above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a system for fabricating a three dimensional structure according to one embodiment.

FIG. 2 is a schematic side view of a printing device of the system of FIG. 1 according to one embodiment.

FIG. 3 is a schematic side view of a printing device of the system of FIG. 1 according to another embodiment.

FIG. 4 is a schematic side view of a printing device of the system of FIG. 1 according to another embodiment.

FIG. 5 is a schematic view of a microstructure of a three dimensional structure according to one embodiment.

FIG. 6 is a block diagram of a control system for a device for fabricating a three dimensional structure according to one embodiment.

FIG. 7 is a flowchart of a method of fabricating a three dimensional structure according to one embodiment.

FIG. 8 is a flowchart of a method of fabricating a three dimensional structure according to another embodiment.

FIG. 9 is a flowchart of a method of fabricating a three dimensional structure according to another embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here.

Additive manufacturing is a process in which an object is built up layer by layer, with the desired geometry typically being read from a computer file and recreated by extrapolating the geometry into a series of thin layers. The layers may be cut and joined together with a lamination process, formed by selectively curing portions of a substance (e.g., stereolithography, etc.), or formed by transforming a powdered material to a solid mass by melting or otherwise fusing the powdered material together (e.g., selective laser sintering, fused deposition, laser deposition, etc.). Current additive manufacturing processes often do not produce objects with material properties that are suitable for use as a final product. Instead, the objects are often more suitable for display or prototype and proof-of-concept purposes.

Referring to the figures generally, systems and methods for fabricating a metal object with an additive manufacturing process are shown. In some embodiments, additive manufacturing is used to form an object by depositing material at various printing sites, or areas, in succession to eventually form a completed object. The additive manufacturing process can be configured such that the delivery of heating energy, material, cooling, and other processing is controlled locally at each individual printing site (or, alternatively, at sub-areas within an individual printing site). The microstructure of the fabricated object may therefore be controlled at each printing site and/or varied between printing sites to achieve a desired grain size, phase concentration, impurity concentration, pinning point distribution, or other characteristic. In this way, the fabricated object can be engineered to have superior material properties relative to objects provided with more conventional processes.

Referring now to FIG. 1, printing system 10 (e.g., an additive manufacturing system, etc.) configured to fabricate a metal structure is shown according to one embodiment. Printing system 10 includes printing device 12 (e.g., an additive or 3D printing device, etc.) operated by control system 14. Printing system 10 can form object 18 using digital data, such as a 3D computer-aided design (CAD) model. Control system 14 may receive additional instructions or data from auxiliary system 16. Auxiliary system 16 may be, for example, an external drive or storage device containing a CAD model and/or other control data. The CAD model may be generated with any suitable CAD program, and may be stored in any suitable digital file format. According to various alternative embodiments, one or both of control system 14 and auxiliary system 16 can be integrated into device 12.

According to one embodiment, printing device 12 includes frame 20 and delivery device 22 movable relative to frame 20 via positioning system 24. Printing device 12 may include a multitude of delivery devices configured to deliver a material (e.g., a powdered metal, a metal wire, a liquid metal, etc.) to form object 18, as well as heating energy, cooling, agitation, or other means of manipulating the material, as described in more detail below. Printing device 12 forms object 18 by delivering and manipulating the material at successive printing sites 19 (e.g. printing zones or areas, work zones, delivery zones, fabrication zones, etc.). Object 18 is formed in interior 38 of printing device 12. Interior 38 is defined by sidewalls 36. According to one embodiment, interior 38 can be a sealed interior, which can have characteristics different from the characteristics of the surrounding environment. For example, the temperature, pressure, or other characteristics (e.g., composition of atmospheric gases, etc.) of interior 38 can be controlled to facilitate improved fabrication of object 18. According to one embodiment, interior 38 can be maintained at a partial vacuum or in an atmosphere of an inert gas (e.g., argon, helium, etc.).

According to one embodiment, positioning system 24 is configured to position delivery device 22 using, for example, coordinates provided to printing device 12 from control system 14. Positioning system 24 can use a Cartesian coordinate system, with delivery device 22 movable via carriage system 26. Carriage system 26 includes a rail oriented in the X direction and a rail in the Y direction (providing X-Y horizontal movement), and a vertical adjustment member 28 (providing Z direction vertical movement).

Object 18 is supported by object support platform 30, which is in turn supported by frame 20. Platform 30 can be coupled to frame 20 via positioning system 32. Positioning system 32 can be configured to position support platform 30 using coordinates provided to printing device 12 from control system 14. According to one embodiment, support platform 30 is movable relative to frame 20 on a horizontal X-Y plane through carriage system 34. According to a further embodiment, support platform 30 is further movable in a vertical direction using a vertical adjustment member (e.g., a vertical adjustment member similar to vertical adjustment member 28, etc.). According to another embodiment, support platform 30 may not be movable and may instead be rigidly coupled to frame 20.

According to another embodiment, rather than using an X-Y-Z Cartesian coordinate system, positioning systems 24 and 32 may use an alternative coordinate system, such as a cylindrical coordinate system, to position delivery device 22 and/or support platform 30. According to other embodiments, positioning systems 24 and 32 may be configured to tilt or rotate support platform 30 or delivery device 22 about any of the X, Y, Z, or another positioning axis.

Positioning systems 24, 32 are configured to properly position object 18 relative to delivery device 22 during the 3D printing of object 18. Object 18 is formed through an additive process, with material being selectively added to object 18 by delivery device 22 at printing site 19. The added material is joined together or fused with material in neighboring printing sites (e.g., material below the printing site 19 on another plane, material surrounding the printing site 19 on the same plane, etc.) to form a solid object.

Referring now to FIG. 2, a portion of printing device 50 is shown according to one embodiment as a laser deposition device. Printing device 50 can be incorporated into a 3D printing system such as system 10 or a similar system. Printing device 50 forms object 52 supported by platform 54. Object 52 is formed from material 56 delivered from first delivery device 58 to printing site 60. Material 56 is melted by heating energy 62 delivered to printing site 60 from first delivery device 58 (e.g., via a laser, etc.). According to one embodiment, material 56 can be melted by heating energy 62 (e.g., heat or energy provided as radiant energy, etc.) and manipulated during and/or after the application of heating energy 62 with coolant 64 delivered to the printing site 60 from second delivery device 66, and/or energy such as ultrasonic vibrations generated by a transducer shown as agitation device 68. The manipulation of material 56 during formation at printing site 60 enables the controlled formation of a desired microstructure of material 56.

According to one embodiment, material 56 is or includes a powdered metal material (e.g., tool steel, stainless steel (e.g., 420, 316, 304, etc.), nickel alloys, cobalt alloys, titanium alloys, etc.). The powdered metal is supplied to first delivery device 58 from a supply (e.g., hopper, feeder, bin, etc.). The powdered metal is ejected from first delivery device 58 from one or more nozzles 59. Multiple nozzles 59 can be angled relative to one another to focus the streams of material 56 at printing site 60 spaced a distance away from first delivery device 58. The flow rate of material 56 and the speed at which first delivery device 58 is moved relative to object 52 can be controlled to achieve a desired thickness for each printing site and/or layer of material forming object 52.

While in some embodiments, material 56 is delivered to printing site 60 as a metal powder, according to other embodiments, material 56 may be a metal delivered in another form. For example, material 56 may be a solid metal delivered as a wire fed from first delivery device 58 to printing site 60, or alternatively, may be a liquid metal delivered as a liquid metal stream or jet from first delivery device 58 to printing site 60. Material 56 can be delivered in various other forms according to various alternative embodiments.

According to further embodiments, material 56 may be provided by material streams from several different supplies. For example, a primary material may be mixed with additives, such as particles configured to act as catalysts for nucleation, or grain refiners configured to retard the growth of dendritic grains. In other embodiments, material 56 may be provided by different elemental streams, with the flow rate of the different streams varied during the fabrication of object 52 to achieve different alloy compositions in different portions of object 52.

According to one embodiment, first delivery device 58 is configured to provide a first material at a first printing site and a second material at a second printing site. For example, the amount of material, the rate of deposition of material, the composition of the material, or other parameters may be varied between the first material delivered to the first printing site and the second material delivered to the second printing site. Varying various parameters associated with the delivery of material to different printing sites enables variation of the microstructure (e.g., grain structure, etc.) between printing sites.

Referring further to FIG. 2, in one embodiment, heating energy 62 is provided by a laser directed at printing site 60 by first delivery device 58. The laser may be any suitable laser capable of providing the heating energy needed to melt material 56. For example, the laser may be a fiber laser with an optical fiber doped with a rare-earth element (e.g., erbium, ytterbium, neodymium, etc.), another type of solid-state laser, or a gas laser. In some embodiments, first delivery device 58 may further provide a volume (e.g., envelope, sleeve, etc.) of a shielding gas surrounding the laser and/or material 56 that differs from the atmosphere in the interior of the printing device to provide a more favorable environment for the fabrication of object 52 (e.g., to limit oxidation, etc.).

The laser provided by first delivery device 58 is configured to generate a “melt pool” of molten material, and provide precise control of the size and depth of the melt pool. As such, a relatively narrow heat-affected zone surrounds the melt pool, thereby minimizing thermal distortion of the portions of object 52 surrounding printing site 60. Printing site 60 can be heated by any method or combination of methods, including through the use of a laser. According to other embodiments, heating energy 62 can be provided via first delivery device 58 in another form, such as an electron beam or a micro-arc. According to still another embodiment, heating energy 62 can be delivered to printing site 60 through conduction by local resistance heating of object 52, by thermal conduction from a (small) heat source contacting printing site 60, or by controlling the temperature of material 56 delivered to printing site 60.

In one embodiment, first delivery device 58 focuses heating energy 62 at printing site 60 (e.g., with a lens, etc.), and material 56 melts to form a melt pool. First delivery device 58 forms a bead of material (e.g., a weld bead, etc.) as it is moved relative to platform 54. The bead includes material deposited at successive printing sites, and forms a layer of solidified material on the X-Y plane. The bead may be a continuous bead of material, or alternatively, a non-continuous bead of material. Successive layers of material are fused together to form object 52. By controlling the delivery of heating energy 62 to printing site 60, the melting of material 56 can be controlled. Although controlling only the delivery of heating energy 62 provides some control over the post-melting solidification of material 56 and of the resulting microstructure of object 52, more precise control is possible, as in conventional metal formation, by also controlling the quenching (i.e., the cooling) of the molten metal.

According to one embodiment, first delivery device 58 is configured to vary the heating energy provided to first and second printing sites. For example, the amount of heating energy, the intensity of heating energy, the delivery method, or other parameters may be varied between the first and second printing sites. Varying various parameters associated with the delivery of heating energy to different printing sites enables variation of the microstructure (e.g., grain structure, etc.) between printing sites.

In one embodiment, the microstructure of object 52 is further controlled through cooling of the melt pool (e.g., material 56) at printing site 60. For example, a coolant 64 can be locally delivered by second delivery device 66. Second delivery device 66 can be any mechanism suitable for the delivery of coolant 64 to printing site 60. Coolant 64 can be delivered directly to printing site 60, or alternatively, can be delivered indirectly to printing site 60 by, for example, cooling areas of object 52 surrounding printing site 60 (i.e., neighboring printing sites) or by cooling platform 54 supporting object 52. By locally cooling printing site 60, the microstructure of different portions of object 52 can be individually controlled and/or varied.

The material at printing site 60 is locally cooled in a controlled manner, either through the direct or indirect cooling of the material. Local, controlled cooling allows the quenching of the material to be controlled to a greater degree than, for example, bulk cooling object 52, or allowing object 52 to cool slowly to room temperature. Controlling the quenching of the material enables for the controlled formation of a desired microstructure (e.g., the transformation of austenite to martensite in steel, etc.) in object 52. In some embodiments, the delivery of coolant 64 can be delayed to allow the material to remain at an elevated temperature for a period of time.

Printing site 60 can be locally cooled by thermal conduction to a small cooling probe such as a thermoelectric cooler, a heat pipe, a mini-cooling loop, or the like. In other embodiments, printing site 60 can be cooled by applying coolant 64 which absorbs energy from printing site 60. Coolant 64 can respond to the absorbed heat by increasing its temperature (i.e., via its specific heat) and/or by undergoing a phase change (i.e., via latent heat). A vaporizable liquid coolant provides an effective embodiment of coolant 64, because vaporization of the liquid provides an efficient way to absorb heat and because the coolant is directly removed from the site as it vaporizes, without leaving residuals. Coolant 64 can be a liquid with a relatively low boiling point, or alternatively, a liquid with a relatively high boiling point, with coolant 64 chosen such that the boiling point of coolant 64 corresponds to a desired quench temperature and/or cooling rate for the material at printing site 60. Coolant 64 can be or include water, alcohol, an oil, a solvent, or a liquid metal, including, but not limited to, sodium, sodium-potassium alloy, sodium-lithium alloy, lithium, or a mixture of liquid metals. In some embodiments, the boiling point of coolant 64 can be varied by controlling the pressure of the interior of printing device 50, by modifying the composition of coolant 64, etc.

According to one embodiment, delivery device 66 is configured to deliver a high-speed stream of coolant 64 in the form of a vaporizable liquid to printing site 60. According to another embodiment, delivery device 66 is an atomizer configured to deliver liquid coolant 64 as a mist. According to yet another embodiment, delivery device 66 is or includes a device such as a wick, brush, or tube that directs a low-speed stream of a liquid coolant to printing site 60. According to a further embodiment, delivery device 66 can be a fan configured to direct a stream of coolant 64 in the form of a gas (e.g., air, an inert gas, etc.) at printing site 60 to cool material by convection. According to various alternative embodiments, combinations of one or more coolant delivery devices can be used to deliver coolant 64.

In one embodiment, coolant 64 is not delivered directly to material to printing site 60, but rather is provided as a part of a heat pipe or similar system incorporated into or separate from delivery device 66. A heat pipe can include a casing with a first end proximate the melt pool at printing site 60 (e.g., on the surface of the object 52). The first end of the heat pipe absorbs heat through the walls of the casing and vaporizes a liquefied coolant contained within the casing. The vaporized coolant releases latent heat at a second end and condenses back to a liquid. One or both ends of the heat pipe can include features such as a heat sink to facilitate the transfer of heat between the outside environment and the coolant contained within the heat pipe. The coolant contained within the heat pipe can be chosen to achieve a preferred heat transfer from printing site 60. The internal pressure of the heat pipe can also be chosen and/or varied to control the phase changes of the coolant and further control the heat transfer from the printing site.

According to one embodiment, coolant 64 can be delivered continuously to printing site 60. Alternatively, coolant 64 can be delivered intermittently (e.g., in a digital manner, etc.) to printing site 60 to achieve a desired microstructure. Various coolants, delivery devices, and delivery durations may be utilized for object 52 to form a metallic structure with varied microstructures. In some embodiments, delivery device 66 can be operated based on feedback data collected from sensors monitoring the fabrication of object 52, as described in more detail below.

Printing device 50 may further include a system for removing coolant (e.g., vaporized or heated liquid coolant) from the surface of object 52 or the interior of printing device 50, after the coolant has been utilized to cool printing site 60. For example, printing device 50 may include a gas circulation system (e.g., incorporated into delivery device 66 or another component of the printing system) configured to remove gas from the interior of printing device 50 through an outlet duct and introduce gas to the interior of the printing device through an inlet duct. After being removed from the interior of printing device 50, the gas may be scrubbed, cooled or otherwise processed and returned back to the interior of printing device 50. Printing device 50 may include multiple inlet and outlet ducts such that the ducts can be opened, closed, or reversed to advantageously control the movement of gas within the interior of printing device 50 and across the surface of object 52, including proximate printing site 60.

According to one embodiment, delivery device 66 is configured to provide a first coolant to a first printing site and a second coolant to a second printing site. For example, the type of coolant, the amount of coolant, the timing or rate of delivery of coolant, the predefined delivery temperature of the coolant, the composition of the coolant, or other parameters may be varied between the first and second printing sites. In some embodiments, the delivery of heating energy (e.g., from delivery device 58) may be interrupted during the delivery of the coolant. In some embodiments, the delivery of coolant can be nonsimultaneous with the delivery of heating energy at a site. In some embodiments, the delivery of coolant can begin after the delivery of heat energy begins at a site. In some embodiments the delivery of coolant can continue after the delivery of heat energy has stopped at a site. Varying various parameters associated with the delivery of coolant to different printing sites enables variation of the microstructure (e.g., grain structure, etc.) between printing sites.

In some embodiments, the microstructure of object 52 is further controlled by subjecting the material at printing site 60 to agitation, such as by sound waves (e.g., acoustic waves, ultrasonic waves, etc.). According to one embodiment, the waves are generated by agitation device 68 (e.g., agitator, wave generator, etc.) and directed at object 52. Agitation device 68 is positioned and configured to direct the waves to printing site 60 to induce local vibration in object 52. According to various alternative embodiments, agitation device 68 can be a piezoelectric transducer, a magnetostrictive transducer, a surface acoustic wave (SAW) generator, a bulk acoustic wave (BAW) generator, or a standing wave field generator (e.g., an ultrasonic wave field generator, etc.). According to one embodiment, as shown in FIG. 2, agitation device 68 can be positioned remote from printing site 60 and can be configured such that the waves are steered to or focused at printing site 60. Wave generation and steering and/or focusing can utilize a coherent array of wave generators (e.g., with phase and/or amplitude control of each); phase conjugation can be used to help control such remote wave delivery. According to another embodiment, agitation device 68 can be positioned proximate to printing site 60.

In one embodiment, agitation device 68 provides ultrasonic vibrations to printing site 60. Ultrasonic vibrations applied to a solidifying metal or alloy can decrease the size of the grains, increase the soundness of the grains, and/or decrease the occurrence of dendritic grain formation in the material. When molten material in the melt pool at printing site 60 is near the melting point (for a pure metal) or liquidus temperature (for an alloy), ultrasonic waves can influence the formation of solid nuclei, which leads to the corresponding formation of grains in the solidifying material, the grains being increased in number and decreased in size.

The amplitude and frequency of the waves produced by agitation device 68 can be controlled to produce grains of a desired size. According to one embodiment, agitation device 68 is configured to produce waves with a frequency selected based on a desired microstructure (e.g., grain size, etc.). The frequency produced by agitation device 68 can be maintained at a constant level for the entire fabrication process, or alternatively, can be altered to facilitate the growth of grains of different desired sizes in different portions of object 52. The wavelength of the waves produced by agitation device 68 can also be configured to produce grains of a desired size. In some embodiments, the delivery of waves can be nonsimultaneous with the delivery of heating energy at a site. In some embodiments, the delivery of waves can begin after the delivery of heat energy begins at a site. In some embodiments, the delivery of waves can continue after the delivery of heat energy has stopped at a site, e.g., to perform ultrasonic peening. In some embodiments, agitation device 68 may be operated based on feedback data collected from sensors monitoring the fabrication of object 52, as described in more detail below.

According to one embodiment, agitation device 68 is configured to provide differing waves to induce different vibrations at first and second printing sites. For example, the amplitude, wavelength, or other parameters associated with the delivery of the waves may be varied between the first and second printing sites. Varying various parameters associated with providing vibrations to different printing sites enables variation of the microstructure (e.g., grain structure, etc.) between printing sites.

According to one embodiment, the microstructure of object 52 can be further controlled by subjecting the material in the melt pool at printing site 60 to other processing or conditions. For example, magnet 69 can be provided proximate to printing site 60. Magnet 69 produces a magnetic field that passes through printing site 60. For magnetic materials (e.g., many steel alloys) the magnetic field influences the grain formation as the material in the melt pool solidifies and cools. Magnet 69 can be a permanent magnet generating a constant magnetic field, or may be a variable magnet (e.g., an electromagnet) that can be controlled to produce a variable magnetic field.

Referring further to FIG. 2, in some embodiments, printing site 60 is monitored to provide feedback data to printing device 12. The data may then be utilized by printing device 12 to control the printing process to achieve the desired microstructure in object 52. According to one embodiment, printing device 50 may include image monitoring device 70, and one or more sensors 72 to collect data from printing site 60.

In one embodiment, image monitoring device 70 (e.g., an image capturing device, etc.) is configured to monitor the microstructure of object 52. Image monitoring device 70 can be an optical microscope, an electron microscope, an x-ray microscope, etc. Optical microscopes can be used to examine relatively large microstructures, while electron microscopes and x-ray microscopes can be used to examine relatively small images (e.g., features or structures smaller than approximately one half micron). Image monitoring device 70 may include multiple devices, allowing the microstructure of object 52 to be examined at different scales simultaneously. Image monitoring device 70 captures an image (e.g., a still image or a video) of object 52. The image may be transferred to an analysis device and be utilized to collect data concerning the microstructure at printing site 60, such as an average grain size, or the formation of various phases of the material. According to one embodiment, image monitoring device 70 captures images of object 52 after the material at printing site 60 has solidified. Image monitoring device 70 may therefore be configured to capture images of an area trailing the current printing site 60. Image monitoring device 70 may be configured to collect further visual data, such as by capturing an image of a portion of object 52 surrounding the current printing site 60. The additional image data may be utilized, for example, to monitor the heat-induced distortions in the microstructure of object 52 surrounding printing site 60, as caused by the heating energy provided to create the melt pool at printing site 60.

Sensors 72 may be configured to collect a wide variety of data concerning the portions of object 52 at printing site 60. According to one embodiment, sensor 72 can be or include a thermometer configured to monitor the temperature of printing site 60 or the portion of object 52 surrounding printing site 60. For example, sensor 72 may be a contact thermometer, such as a thermocouple in direct contact with object 52, or may be a non-contact thermometer, such as an infrared thermometer that is disposed away from object 52. Sensor 72 may be an array of multiple thermometers configured to monitor the temperature at several locations at and/or surrounding printing site 60. According to another embodiment, sensor 72 can be or include a vibration transducer configured to monitor the longitudinal or shear waves produced by agitation device 68. According to other embodiments, sensor 72 may include multiple types of sensors that operate together to monitor multiple phenomena related to the solidification of the material forming object 52.

Referring now to FIG. 3, a portion of printing device 80 is shown according to one embodiment as a laser deposition device. Printing device 80 forms object 82 supported by a platform 84 in a manner similar to the printing device 50 shown and discussed with respect to FIG. 2. Object 82 is formed from a material 86 delivered from a first delivery device 87 to printing site 90. Material 86 is melted by heating energy 92 delivered to printing site 90 from a second delivery device 89. According to one embodiment, material 86 is manipulated during and/or after the application of heating energy 92 with substances such as coolant 94 delivered to printing site 90 from third delivery device 97, energy such as vibrations generated by agitation device 98, or by a magnetic field generated by magnet 99. The delivery of material 86 and heating energy 92 via separate delivery devices 87 and 89 may advantageously provide for the improved melting of material 86 and/or creation of a melt pool at printing site 90.

According to one embodiment, the additive manufacturing system is configured to provide, or define, different microstructure at or within different portions of an object. For example, as discussed in greater detail below, one or more image capture devices, sensors, etc. may be configured to provide feedback regarding the formation of an object, and in response, one or more parameters associated with the delivery of material, heating energy, vibrations, coolant, etc. can be varied between printing sites.

After being formed with a printing process, the fabricated object may be subjected to further processing, such as heat treating (e.g., annealing, tempering, etc.) and the like. Such post-printing processing enables further altering of the microstructure and the mechanical properties of the material beyond what may be possible during the 3D printing process.

Referring now to FIG. 4, a schematic top view of a portion of printed metal object 100 is shown according to one embodiment. Material from delivery device 102 is melted and solidified at printing site 104. In one embodiment, as delivery device 102 is moved relative to object 100, bead 106 of solidified material is formed on the surface of object 100 (the surface of the object being material printed at previous print sites and/or in previous layers). By controlling the delivery of material and heating energy to printing site 104, as well as the delivery of ultrasonic or acoustic waves and the rate of cooling through the delivery of a coolant, the mechanical properties of object 100 can be controlled. The heat affected zone 108 can be minimized by providing heating energy to printing site 104 in the form of a laser or an electron beam. Locally controlling the heating energy, material, agitation, cooling, and other factors, as opposed to subjecting the entirety of object 100 to “bulk” conditions (e.g., with a bulk cooling process, etc.), allows the mechanical properties of object 100 to be varied between different areas/printing sites of object 100. Mechanical properties may be further controlled within different portions of printing site 104 (e.g., local cooling or quenching of material may generate a microstructure in center 110 of printing site 104 that is different than the microstructure at the periphery of printing site 104).

Referring now to FIG. 5, an example microstructure of an object formed by the printing devices disclosed herein is shown. A desired microstructure is created by locally controlling the heating energy, material, agitation, cooling, and other factors as the material is printed, thereby allowing the fabricated object to have desired mechanical properties (e.g., strength, toughness, ductility, hardness, etc.). According to one embodiment, the microstructure is configured to have a relatively small grain structure including a multitude of small grains 120 (e.g., crystallites) separated by grain boundaries 122. Grain boundaries 122 represent disconnects between crystal lattices of neighboring grains 120, and impede the movement of dislocations through the material. A fine grain structure increases the number of grain boundaries 122, and increases the yield strength of the material. A large grain structure, conversely, lowers the yield strength of the material, but increases ductility and electrical and thermal conductivity. Local control of heating energy, material, agitation, cooling, and other factors allows the grain structure to be written, or printed, as desired, allowing different portions of the manufactured object to have different mechanical properties. The local control of the printing process may also be used to vary the mechanical properties of the material in other ways, such as by varying the presence and/or concentrations of different phases of the material, the presence and/or concentration of dislocations, pinning points, impurities, etc.

Referring now to FIG. 6, a schematic block diagram of printing system 130 is shown according to one embodiment. Printing system 130 includes 3D printing device 132 operated by control system 134. Printing device 132 forms an object using digital data, such as a 3D computer-aided design (CAD) model. Printing device 132 can be the same or similar to any of the other printing devices discussed herein. Furthermore, printing system 130 may include one or more auxiliary systems 136 (e.g., computer systems, etc.).

According to one embodiment, control system 134 includes processor 140 and memory 142. Processor 140 may be implemented on a chip, integrated circuit, circuit board, etc., as a general purpose processor, an application specific integrated circuit (ASIC), one or more field programmable gate arrays (FPGAs), a group of processing components, or other suitable electronic processing components. Memory 142 can be or include one or more devices (e.g., RAM, ROM, Flash memory, hard disk storage, etc.) for storing data and/or computer code for completing and/or facilitating the various processes described herein. Memory 142 can be or include non-transient volatile memory or non-volatile memory or non-transitory computer readable storage media. Memory 142 can include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described herein. Memory 142 can be communicably connected to the processor and include computer code or instructions executable by the processor for executing one or more processes described herein. Control system 134 can include one or more modules configured to use data and code stored in memory 142 to execute a process via processor 140.

Control system 134 further includes input device 144 and output device 146. Input device 144 can be a mouse, keyboard, trackball, touchscreen or any other device that allows a user to input instructions to control system 134. Input device 144 can be used, for example, in combination with a graphical user interface to allow a user to control various parameters associated with the operation and monitoring of printing device 132 or auxiliary systems 136. Output device 146 can be a visual output device, such as a monitor (e.g., a CRT monitor, LCD monitor, LED monitor, etc.), an audio device, or another device.

Control system 134 can receive additional instructions or data from auxiliary system 136. Auxiliary system 136 can be, for example, an external drive or storage device containing the CAD model and other control data. The CAD model can be generated with any suitable CAD program and can be stored in any suitable digital file format. The geometry of the CAD model is analyzed and divided into a multitude of slices, layers, or portions that correspond to portions to be printed by printing device 132.

As shown in FIG. 6, printing device 132 includes positioning system 150, material delivery system 152, heating energy delivery system 154, coolant delivery system 156, and agitation system 158. Positioning system 150 controls the positions of the delivery devices relative to the platform on which the object is fabricated, and can be or include any of the positioning systems discussed herein. Positioning system 150 controls the delivery devices to form a bead of material in a desired path on the X-Y plane. In some embodiments, multiple passes of the delivery device in the X-Y (horizontal) plane forms a slice or layer of the object as defined by the CAD model. Movement of the delivery devices in the Z (vertical) direction positions the delivery devices to form successive layers. According to one embodiment, positioning system 150 may further control the position of the platform on which the object is formed, either in addition to or instead of controlling the position of the delivery devices. Positioning system 150 may further control the orientation of the delivery devices and/or the platform through rotation about one or more axis (e.g., the X-axis, Y-axis, Z-axis, etc.).

Material delivery system 152 controls the delivery of material from a supply to the printing site via a material delivery device, and can include any of the material delivery devices discussed herein. Material delivery system 152 can, for example, control the flow rate of a powdered or a liquid metal or the feed rate for a solid wire to the printing site. Material delivery system 152 can control the delivery ratio of two or more materials to a printing site to alter the composition of the material of different portions of the fabricated object. As such, different materials can be delivered to different printing sites of an object.

Heating energy delivery system 154 controls the delivery of heating energy to the printing site via a heating energy delivery device, and can include any of the heating energy delivery devices discussed herein. Heating energy delivery system 154 can control the operation of a laser, including focusing the laser at the printing site and controlling the power output of the laser. The heating energy delivery system 154 can operate the laser to provide continuous heating energy to the printing site, or can activate and deactivate the laser to provide intermittent heating energy to the printing site. According to other embodiments, heating energy delivery system 154 can be configured to control an electron beam or another heating energy delivery device, such as resistance heater configured to supply an electrical voltage applied to the object to heat the printing site by resistance heating.

Coolant delivery system 156 controls the delivery of coolant (e.g., a liquid or gas coolant) to the printing site via a coolant delivery device to reduce the temperature of the material at a desired rate, and can include any of the coolant delivery devices discussed herein. For example, coolant delivery system 156 can control the flow rate of a high pressure stream of a liquid coolant directed at the printing site or at a portion of the fabricated object proximate to the printing site. Coolant delivery system 156 can vary the type of coolant delivered or the rate/amount of coolant delivered depending on the material used and the desired cooling time. In some embodiments, the delivery of coolant can be delayed to allow the material to remain at an elevated temperature for a period of time.

Agitation system 158 controls the generation and delivery of sound energy to the printing site. Agitation system 158 can operate an agitation device (e.g., agitator, wave generator, etc.) to generate ultrasonic or acoustic waves at a desired amplitude and frequency, and can include any of the agitation devices discussed herein. Agitation system 158 can be configured to continuously generate waves, or alternatively, can be configured to engage and disengage the agitation device to intermittently generate waves.

Printing device 132 can further include other systems 159. Other systems 159 can be utilized to, for example, control a magnet (e.g., an electromagnet) to generate a desired magnetic field at the printing site, or any other suitable device. Furthermore, it should be noted that according to various alternative embodiments, one or both of systems 156, 158 may be omitted.

Printing device 132 further includes a monitoring system 160 for monitoring the operation of the other systems of printing device 132 and the object fabricated by printing device 132. Monitoring system 160 can be configured to visually monitor the printing site and the portions of the object surrounding the printing site. Monitoring system 160 can adjust the focus and/or magnification of a monitoring device (e.g., an optical microscope, electron microscope, etc.) to obtain an image of the microstructure of the material. In one embodiment, monitoring system 160 is configured to collect other data, such as pressure data (e.g., to monitor ultrasonic vibrations) and temperature, with a variety of sensors. The sensors can be positioned on the surface of the fabricated object or away from the object. The sensors are configured to collect data from the printing site, a portion of the object near the printing site, an area of the object away from the printing site, or the interior of the printing device. Data collected by monitoring system 160 is used to provide feedback on the formation of the object. The data can be used to adjust the parameters of one of the other systems (e.g., positioning system 150, material delivery system 152, heating energy delivery system 154, coolant delivery system 156, agitation system 158 or other systems 159) to adjust the microstructure of the object. The adjustments can be initiated automatically (e.g., by processor 140) or alternatively can be initiated manually (e.g., by a user with input device 144). For example, in one embodiment, processor 140 receives inputs from monitoring system 160 (e.g., temperature data, pressure data, etc.), and provides control signals to one or more of systems 150, 152, 154, 156, 158, and 159 based on the inputs.

Referring now to FIG. 7, method 170 of fabricating a 3D metal structure with an additive manufacturing system is shown according to one embodiment. A material (e.g., material 56 or material 86) is delivered to a printing site (172). According to various embodiments, the amount, location, type, etc. of material provided can be controlled, and can vary within and between printing sites. Heating energy (e.g., heating energy 62 or heating energy 92) is delivered to the printing site (174). As discussed above, heating energy can be provided in a variety of ways, and the amount of heating energy and other parameters can be varied within and between printing sites. The printing site is agitated (e.g., by way of ultrasonic or acoustic waves generated by agitation device 68 or agitation device 98) (176). For example, various types of ultrasonic waves can be continuously and/or intermittently provided, and various characteristics of the waves (e.g., frequency, amplitude, etc.) can be varied within and between printing sites. The resulting properties of the fabricated metal structure are then monitored and the data is utilized to adjust the control parameters for the delivery of material, heating energy, and agitation to the printing site, or alternatively, to a subsequently printed portion of the printing site or a subsequently printed printing site (178). The process can then continue for subsequent printing sites until the object is formed.

Referring now to FIG. 8, method 180 of fabricating a 3D metal structure using an additive manufacturing system is shown according to another embodiment. Material (e.g., material 56 or material 86) is delivered to a printing site (182). Heating energy (e.g., heating energy 62 or heating energy 92) is delivered to the printing site (184). The delivery of material and/or heating energy to the printing site can be controlled in a manner similar to that discussed with respect of FIG. 7. A coolant (e.g., coolant 64 or coolant 94) is delivered to the printing site (186). The amount, location, type etc. of coolant provided can be varied within and between printing sites. The resulting properties of the fabricated metal structure are then monitored and the data is utilized to adjust the control parameters for the delivery of material, heating energy, and coolant to the printing site, or alternatively, to a subsequently printed portion of the printing site or a subsequently printed printing site (188).

Referring now to FIG. 9, method 190 of fabricating a 3D metal structure using an additive manufacturing system is shown according to another embodiment. Material (e.g., material 56 or material 86) is delivered to a printing site (192). Heating energy (e.g., heating energy 62 or heating energy 92) is delivered to the printing site (194). The printing site is agitated (e.g., by way of ultrasonic or acoustic waves generated by agitation device 68 or agitation device 98) (195). A coolant (e.g., coolant 64 or coolant 94) is delivered to the printing site (196). Other process parameters, such as the delivery of a magnetic field, etc. to the printing site can further be controlled (197). The resulting properties of the fabricated metal structure are then monitored and the data is utilized to adjust the control parameters for the delivery of material, heating energy, agitation, coolant and other processes (198). The method illustrated in FIG. 9 may control the delivery of material, heating energy, agitation, coolant, or other processes in a manner similar to that discussed with respect of FIGS. 7 and 8.

While the systems and methods described herein relate to the fabrication of a metal part with laser deposition or similar technology, the local control of printing variables, along with monitoring and feedback systems, may be useful for other additive manufacturing processes involving metals or non-metals. For example, a selective laser sintering process may be utilized to form an object, and the process can be monitored to detect the size and concentration of pores in the fabricated object. This data may then be utilized to control, for example, the power output of the laser to achieve a desired final product. The systems and methods disclosed herein may be used in combination with other fabrication techniques according to various other alternative embodiments.

The present disclosure contemplates methods, systems, and program products on any machine-readable media for accomplishing various operations. The embodiments of the present disclosure may be implemented using existing computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwired system. Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a machine, the machine properly views the connection as a machine-readable medium. Thus, any such connection is properly termed a machine-readable medium. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions.

Although the figures may show a specific order of method steps, the order of the steps may differ from what is depicted. Also two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims. 

1. A method of fabricating a three dimensional structure, comprising: delivering a metal material to a printing site; and defining a microstructure of the metal material at the printing site by: controlling the delivery of heating energy to the printing site; and controlling the delivery of ultrasonic vibrations to the printing site.
 2. The method of claim 1, wherein delivering the metal material to the printing site includes delivering a metal powder to the printing site.
 3. The method of claim 1, wherein delivering the metal material to the printing site includes delivering a metal wire to the printing site.
 4. The method of claim 1, wherein delivering the metal material to the printing site includes using a liquid metal jet.
 5. (canceled)
 6. The method of claim 1, wherein the heating energy is delivered to the printing site by a laser.
 7. The method of claim 1, wherein the heating energy is delivered to the printing site by an electron beam. 8-18. (canceled)
 19. The method of claim 1, further comprising monitoring a temperature at the printing site and controlling delivery of at least one of the heating energy and the ultrasonic vibrations based on the temperature. 20-22. (canceled)
 23. The method of claim 1, wherein defining the microstructure includes defining a grain boundary.
 24. The method of claim 1, wherein defining the microstructure includes defining a grain size.
 25. The method of claim 1, wherein defining the microstructure includes defining a pinning point for the microstructure. 26-27. (canceled)
 28. The method of claim 1, further comprising delivering a vaporizable coolant to the printing site. 29-47. (canceled)
 48. The method of claim 28, further comprising varying the pattern of delivery of the vaporizable coolant between different portions of the metal at the printing site.
 49. The method of claim 28, further comprising varying an amount of vaporizable coolant delivered to different portions of the metal at the printing site. 50-51. (canceled)
 52. A method of fabricating a three dimensional structure, comprising: delivering a metal material to a printing site; delivering heating energy to the printing site; delivering a vaporizable coolant to the printing site; and defining a microstructure for the three dimensional structure based on providing the heating energy to the metal material at the printing site and vaporizing the vaporizable coolant. 53-76. (canceled)
 77. The method of claim 52, wherein the boiling point of the vaporizable coolant corresponds to a predetermined quenching temperature for the metal delivered to the printing site.
 78. The method of claim 52, further comprising modifying the boiling point of the vaporizable coolant.
 79. The method of claim 78, wherein modifying the boiling point of the vaporizable coolant includes modifying the composition of the vaporizable coolant.
 80. The method of claim 78, wherein modifying the boiling point of the vaporizable coolant includes modifying a pressure of a delivery environment for the vaporizable coolant.
 81. (canceled)
 82. The method of claim 52, further comprising varying the pattern of delivery of the vaporizable coolant between different portions of the metal at the printing site. 83-90. (canceled)
 91. The method of claim 52, wherein the printing site is a first printing site, the metal material is a first portion of metal material, the heating energy is a first amount of heating energy, and the vaporizable coolant is a first vaporizable coolant, and further comprising: delivering a second portion of metal material to a second printing site; delivering a second amount of heating energy to the second printing site; and delivering a second vaporizable coolant to the second printing site.
 92. The method of claim 91, wherein the first portion of metal material differs from the second portion of metal material in at least one of an amount of metal and a type of metal.
 93. The method of claim 91, wherein the first amount of heating energy differs from the second amount of heating energy in at least one of a duration of delivery of heating energy and an intensity of delivery of heating energy.
 94. The method of claim 91, wherein the first vaporizable coolant varies from the second vaporizable coolant in at least one of a type of coolant, a temperature of coolant, and an amount of coolant.
 95. A method of fabricating a three dimensional structure, comprising: delivering a first metal material to a first printing site; delivering a first amount of heating energy to the first printing site; delivering a first vaporizable coolant to the first printing site; agitating the first printing site; and forming a first portion of a printed metal structure by providing the first amount of heating energy to the first metal material at the first printing site and vaporizing the first vaporizable coolant while agitating the first printing site. 96-104. (canceled)
 105. The method of claim 95, wherein agitating the first printing site includes delivering ultrasonic vibrations to the first printing site by a transducer.
 106. The method of claim 95, wherein agitating the first printing site includes delivering bulk acoustic waves.
 107. The method of claim 95, wherein agitating the first printing site includes delivering surface acoustic waves.
 108. The method of claim 95, wherein agitating the first printing site includes delivering ultrasonic vibrations to the first printing site by phase conjugation. 109-110. (canceled)
 111. The method of claim 95, wherein agitating the first printing site includes generating a standing wave ultrasonic field. 112-115. (canceled)
 116. The method of claim 95, further comprising varying the pattern of delivery of the first vaporizable coolant between different portions of the first printing site.
 117. The method of claim 95, further comprising varying an amount of the first vaporizable coolant delivered to different portions of the first printing site. 118-121. (canceled)
 122. The method of claim 95, further comprising delivering a second metal material, a second amount of heating energy, and a second vaporizable coolant to a second printing site, and agitating the second printing site.
 123. The method of claim 122, wherein the first metal material differs from the second metal material in at least one of an amount of material delivered and a type of material delivered.
 124. The method of claim 122, wherein the first amount of heating energy differs from the second amount of heating energy.
 125. The method of claim 122, wherein the first vaporizable coolant differs from the second vaporizable coolant in at least one of type of coolant, a temperature of coolant, and amount of coolant delivered. 126-242. (canceled) 